18F-FDG PET/CT in Cystic Papillary Thyroid Carcinoma.

ABSTRACT: A 52-year-old woman was evaluated for the appearance of a neck lump and dysphonia. Neck ultrasonography showed a large cystic nodule in the right thyroid lobe, confirmed by fine-needle aspiration cytology. Thyroid function and calcitonin were normal. 18F-FDG PET/TC showed moderate tracer uptake by the outer ring of the large hypodense formation. Right hemithyroidectomy was performed; since intraoperative histology showed an intracystic and invasive papillary thyroid carcinoma, a completion thyroidectomy was done. Definitive histopathology confirmed the intraoperative findings. 18F-FDG PET/CT may be a useful imaging procedure in evaluating patients with cystic thyroid nodules whenever clinical/ultrasonographic features are suspicious for malignancy.

Diagnostic yield of FAP-guided positron emission tomography in thyroid cancer: a systematic review.

Background: Several recent studies have proposed the possible application of positron emission tomography/computed tomography (PET/CT) administering radiolabelled fibroblast-activation protein (FAP) inhibitors for various forms of thyroid cancer (TC), including differentiated TC (DTC), and medullary TC (MTC). Methods: The authors conducted an extensive literature search of original studies examining the effectiveness of FAP-guided PET/CT in patients with TC. The papers included were original publications exploring the use of FAP-targeted molecular imaging in restaging metastatic DTC and MTC patients. Results: A total of 6 studies concerning the diagnostic yield of FAP-targeted PET/CT in TC (274 patients, of which 247 DTC and 27 MTC) were included in this systematic review. The included articles reported high values of FAP-targeted PET/CT detection rates in TC, ranging from 81 to 100% in different anatomical sites and overall superior to the comparative imaging method. Conclusion: Although there are promising results, the existing literature on the diagnostic accuracy of FAP-guided PET in this context is still quite limited. To thoroughly evaluate its potential significance in TC patients, it is needed to conduct prospective randomized multicentric trials.

Reappraising the role of thyroid scintigraphy in the era of TIRADS: A clinically-oriented viewpoint.

Thyroid nodules (TNs) are a common entity, with the majority being benign. Therefore, employing an accurate rule-out strategy in clinical practice is essential. In the thyroid field, the current era is significantly marked by the worldwide diffusion of ultrasound (US)-based malignancy risk stratification systems of TN, usually reported as Thyroid Imaging Reporting And Data System (TIRADS). With the advent of US (and later TIRADS), the role of thyroid scintigraphy (TS) in clinical practice has gradually diminished. The authors of the present paper believe that the role of TS should be reappraised, also considering its essential role in detecting autonomously functioning thyroid nodules and its limited contribution to detecting thyroid cancers. Thus, this document aims to furnish endocrinologists, radiologists, surgeons, and nuclear medicine physicians with practical information to appropriately use TS.

Multimodality imaging features of small bowel cancers complicating Crohn's disease: a pictorial review.

Patients with Crohn's disease (CD) are at increased risk of developing small bowel cancer, since chronic inflammation may trigger the histopathological sequence that begins from low-grade dysplasia of the intestinal epithelium and may eventually lead to malignant transformation. Owing to their location in a portion of the gastrointestinal tract which is not easily accessible to conventional endoscopic techniques, the detection of CD-related small bowel cancers is still a clinical challenge. The radiological features of CD-related small bowel adenocarcinoma (SBA) in patients with CD have been described in some previous studies, including its appearance in both CT and MRI examinations. Radiological signs of active or fibrostenotic CD may be intermixed with those suggesting the presence of CD-related SBA. In CT studies, the most relevant findings consistent with malignant transformation are the presence of a stricture with irregular asymmetric thickening of small bowel walls, loss of mural stratification, and moderate enhancement after intravenous administration of iodinated contrast media, in association with enlarged adjacent mesenteric lymph nodes. Many of the CD-related SBA features that can be observed on CT imaging are similar to those detectable by MRI. This latter modality provides the additional value of the functional characterization of small bowel strictures, thereby helping to distinguish between inflammatory, fibrotic, and malignant stenosis in the setting of active CD. Positron Emission Tomography (PET)/CT enables the metabolic assessment of enlarged mesenteric lymph nodes, and PET/MRI fusion imaging can incorporate morphological, functional and metabolic information into a single set of imaging data, thus overcoming the limitations of the separate assessment of each individual modality. Owing to the low incidence and prevalence of this long-term complication of CD, we believe that a detailed multimodality pictorial essay on this topic, also including the PET-CT and fusion imaging documentation of some cases, would be useful to the medical literature.

Incidence of subclinical and overt hypothyroidism in children treated with [131I]mIBG: a systematic review and meta-analysis.

INTRODUCTION: Treatment with [131I]mIBG is commonly used in pediatric metastatic neuroblastoma (NB); however, unbound [131I]I might be taken up by the thyroid, causing hypothyroidism. To prevent this occurrence, thyroid blockade with iodine salts is commonly used; despite this precaution, thyroid dysfunction still occurs. This review and meta-analysis aim to clarify the mean frequency of hypothyroidism in children with NB treated with [131I]mIBG and to investigate the possible causes. EVIDENCE ACQUISITION: The literature was searched for English-language scientific manuscripts describing the incidence of TSH elevation and overt hypothyroidism in children with NB treated with [131I]mIBG. Preclinical studies, small-case series, and reviews were excluded. A proportion meta-analysis was conducted to test the influence of potentially relevant factors (type and duration of thyroid blockade, year of the study, sample size) on the incidence of TSH elevation/overt hypothyroidism. EVIDENCE SYNTHESIS: Eleven studies were included. The pooled percentage of TSH elevation was 0.41 (95% CI: 0.27-0.55); the duration of the thyroid blockade (P=0.004) was inversely correlated with the incidence of TSH elevation. Moreover, a TSH increase was more common in patients treated with potassium iodide (KI) alone than in those managed with a multi-drug thyroid blockade (P<0.001). The pooled percentage of children requiring hormone replacement therapy was 0.33 (95% CI: 0.16-0.49). As in the case of TSH elevation, a longer duration of the thyroid blockade (P=0.006) and a multi-pronged approach (P<0.001) were associated with a lower incidence of overt hypothyroidism. CONCLUSIONS: Hypothyroidism appears to occur frequently in children treated with [131I]mIBG, which should be monitored closely after the radionuclide treatment to start hormone replacement therapy as soon as needed. The duration, as well as the type of thyroid blockade, seem to influence the incidence of hypothyroidism; however, more data from prospective evaluations are needed.

Determinants of circulating calcitonin value: analysis of thyroid features, demographic data, anthropometric characteristics, comorbidities, medications, and smoking habits in a population with histological full exclusion of medullary thyroid carcinoma.

Objective: Calcitonin (Ctn) measurement is crucial for the early diagnosis of medullary thyroid carcinoma (MTC). However, Ctn levels can be skewed/elevated due to other reasons, and the Ctn upper reference value remains controversial. In this field, studies have heterogeneous settings, published data are controversial, and no evidence has been achieved. The study's aim was to evaluate all previously investigated Ctn determinants in a population with histological exclusion of MTC. Methods: The institutional records from 2010 to 2022 were reviewed to select patients with thyroid nodules who had undergone total thyroidectomy with histological exclusion of MTC and who had tested for Ctn just before surgery. Thyroid features, demographic and anthropometric data, comorbidities, medications, and lifestyle information were collected. Univariate and multivariate analyses were performed. Results: A total of 127 cases were included. The median age for thyroidectomy was 51 years. Median Ctn was 1.04 pg/mL (interquartile range (IQR) 1.04-2.77), with two cases having values above 10 pg/mL. In univariate analysis, Ctn was correlated with gender (p < 0.001), body weight (p = 0.016), height (p = 0.031), body surface area (p = 0.016), thyroid size (p = 0.03), thyroglobulin (p < 0.001), and chronic kidney disease (p < 0.001). After multivariate analysis, the model with the highest accuracy included gender, chronic kidney disease, and thyroid-stimulating hormone (TSH) with an adjusted R-squared of 0.4. Conclusions: This study demonstrates, in a population histologically proven as MTC-free, that the Ctn value is mainly influenced by gender, anthropometric/thyroid features, and chronic kidney disease, with the further impact of TSH.

Appropriate and mindful measurement of serum calcitonin in patients with thyroid nodules. A white paper.

Medullary thyroid carcinoma (MTC) is an infrequent thyroid malignancy that is often diagnosed at advanced stage with consequent poor prognosis. Thus, the earlier the diagnosis of MTC, the better the prognosis. Unfortunately, the preoperative detection of MTC remains challenging in clinical practice. In fact, while ultrasound and fine-needle aspiration cytology have suboptimal performance in this context, measuring serum calcitonin (Ctn), fully recognized as the most reliable test to detect MTC, is not universally accepted as routine test in all patients with thyroid nodule(s). The authors of this paper reappraise critically the matter of Ctn measurement in view of the recent advancements in the literature to point out the essential information to be known, and then to prepare an easy-to-use guide for clinicians to appropriately consider the measurement of serum Ctn during clinical practice.

The evidence-based role of catecholaminergic PET tracers in Neuroblastoma. A systematic review and a head-to-head comparison with mIBG scintigraphy.

BACKGROUND: Molecular imaging is pivotal in staging and response assessment of children with neuroblastoma (NB). [123I]-metaiodobenzylguanidine (mIBG) is the standard imaging method; however, it is characterised by low spatial resolution, time-consuming acquisition procedures and difficult interpretation. Many PET catecholaminergic radiotracers have been proposed as a replacement for [123I]-mIBG, however they have not yet made it into clinical practice. We aimed to review the available literature comparing head-to-head [123I]-mIBG with the most common PET catecholaminergic radiopharmaceuticals. METHODS: We searched the PubMed database for studies performing a head-to-head comparison between [123I]-mIBG and PET radiopharmaceuticals including meta-hydroxyephedrine ([11C]C-HED), 18F-18F-3,4-dihydroxyphenylalanine ([18F]DOPA) [124I]mIBG and Meta-[18F]fluorobenzylguanidine ([18F]mFBG). Review articles, preclinical studies, small case series (< 5 subjects), case reports, and articles not in English were excluded. From each study, the following characteristics were extracted: bibliographic information, technical parameters, and the sensitivity of the procedure according to a patient-based analysis (PBA) and a lesion-based analysis (LBA). RESULTS: Ten studies were selected: two regarding [11C]C-HED, four [18F]DOPA, one [124I]mIBG, and three [18F]mFBG. These studies included 181 patients (range 5-46). For the PBA, the superiority of the PET method was reported in two out of ten studies (both using [18F]DOPA). For LBA, PET detected significantly more lesions than scintigraphy in seven out of ten studies. CONCLUSIONS: PET/CT using catecholaminergic tracers shows superior diagnostic performance than mIBG scintigraphy. However, it is still unknown if such superiority can influence clinical decision-making. Nonetheless, the PET examination appears promising for clinical practice as it offers faster image acquisition, less need for sedation, and a single-day examination.

Reaching the target dose with one single 131 I-mIBG administration in high-risk neuroblastoma: The determinant impact of the primary tumour.

BACKGROUND: 131 I-metaiodobenzylguanidine (131 I-mIBG) effectiveness in children with metastasised neuroblastoma (NB) is linked to the effective dose absorbed by the target; a target of 4 Gy whole-body dose threshold has been proposed. Achieving this dose often requires administering 131 I-mIBG twice back-to-back, which may cause haematological toxicity. In this study, we tried identifying the factors predicting the achievement of 4 Gy whole-body dose with a single radiopharmaceutical administration. MATERIALS AND METHODS: Children affected by metastatic NB and treated with a high 131 I-mIBG activity (>450 MBq (megabecquerel)/kg) were evaluated retrospectively. Kinetics measurements were carried out at multiple time points to estimate the whole-body dose, which was compared with clinical and activity-related parameters. RESULTS: Seventeen children (12 females, median age 3 years, age range: 1.5-6.9 years) were included. Eleven of them still bore the primary tumour. The median whole-body dose was 2.88 Gy (range: 1.63-4.22 Gy). Children with a 'bulky' primary (>30 mL) received a higher whole-body dose than those with smaller or surgically removed primaries (3.42 ± 0.74 vs. 2.48 ± 0.65 Gy, respectively, p = .016). Conversely, the correlation between activity/kg and the whole-body dose was moderate (R: 0.42, p = .093). In the multivariate analysis, the volume of the primary tumour was the most relevant predictor of the whole-body dose (p = .002). CONCLUSIONS: These data suggest that the presence of a bulky primary tumour can significantly prolong the 131 I-mIBG biological half-life, effectively increasing the absorbed whole-body dose. This information could be used to model the administered activity, allowing to attain the target dose without needing a two-step radiopharmaceutical administration.

Does it work in childhood and adolescence? The predictive role of postoperative/preablative stimulated thyroglobulin levels in paediatric thyroid cancer. A systematic review of the literature.

BACKGROUND: Thyroglobulin is a well-established disease marker during follow-up in paediatric differentiated thyroid cancer. However, no conclusive data on the role of endogenously stimulated thyroglobulin after thyroidectomy (ptTg) in predicting disease-specific outcomes are available. This review aims to establish the prognostic value of ptTg in children with DTC. METHODS: Online medical databases were searched for studies evaluating the association between ptTg and disease-specific outcomes in DTC-affected children. Documents not in English, preclinical studies, other review articles, case reports, and small case series were excluded. The risk of bias was assessed with the QUADAS-2 tool. RESULTS: Twelve studies, analysing 1043 children in total, were included in the review. They all had a retrospective design and were published between 2016 and 2022. Of all patients, 1008 (97%) and 849 (81%) had undergone thyroidectomy and RAI, respectively. Eight studies (756 children) evaluated the correlation between ptTg and disease persistence/relapse: six reported a significant association between these parameters; a specific ptTg cut-off (10-14 ng/ml) was identified at the multivariate analysis in three studies. The remaining four studies assessed the link between ptTg levels and disease extension, with three reporting a correlation between ptTg and lung/nodal metastases. DISCUSSION: ptTg is a readily available and inexpensive parameter, bearing a strong prognostic power in identifying disease persistence, relapse, and the presence of metastases in children affected by DTC.

Analysis of image data from the EuroNet PHL-C2 trial indicates a potential reduction in injected F-18 FDG activities in children: a proposal to update the EANM Paediatric Dosage Card.

BACKGROUND: The aim of this work is to provide the currently missing evidence that may allow an update of the Paediatric Dosage Card provided by the European Association of Nuclear Medicine (EANM) for conventional PET/CT systems. METHODS: In a total of 2082 consecutive [18F]FDG-PET scans performed within the EuroNet-PHL-C2 trial, the administered [18F]FDG activity was compared to the activity recommended by the EANM Paediatric Dosage Card. None of these scans had been rejected beforehand by the reference nuclear medicine panel of the trial because of poor image quality. For detailed quality assessment, a subset of 91 [18F]FDG-PET scans, all performed in different patients at staging, was selected according to pre-defined criteria, which (a) included only patients who had received substantially lower activities than those recommended by the EANM Paediatric Dosage Card, and (b) included as wide a range of different PET systems and imaging parameters as possible to ensure that the conclusions drawn in this work are as generally valid as possible. The image quality of the subset was evaluated visually by two independent readers using a quality scoring system as well as analytically based on a volume-of-interest analysis in 244 lesions and the healthy liver. Finally, recommendations for an update of the EANM Paediatric Dosage Card were derived based on the available data. RESULTS: The activity recommended by the EANM Paediatric Dosage Card was undercut by a median of 99.4 MBq in 1960 [18F]FDG-PET scans and exceeded by a median of 15.1 MBq in 119 scans. In the subset analysis (n = 91), all image data were visually classified as clinically useful. In addition, only a very weak correlation (r = 0.06) between activity reduction and tumour-to-background ratio was found. Due to the intended heterogeneity of the dataset, the noise could not be analysed statistically sound as the high range of different imaging variables resulted in very small subsets. Finally, a suggestion for an update of the EANM Paediatric Dosage Card was developed, based on the analysis presented, resulting in a mean activity reduction by 39%. CONCLUSION: The results of this work allow for a conservative update of the EANM Paediatric Dosage Card for [18F]FDG-PET/CT scans performed with conventional PET/CT systems.

Molecular imaging and related therapeutic options for medullary thyroid carcinoma: state of the art and future opportunities.

Due to its rarity and non-specific clinical presentation, accurate diagnosis, and optimal therapeutic strategy of medullary thyroid carcinoma (MTC) remain challenging. Molecular imaging provides valuable tools for early disease detection, monitoring treatment response, and guiding personalized therapies. By enabling the visualization of molecular and cellular processes, these techniques contribute to a deeper understanding of disease mechanisms and the development of more effective clinical interventions. Different nuclear imaging techniques have been studied for assessing MTC, and among them, PET/CT utilizing multiple radiotracers has emerged as the most effective imaging method in clinical practice. This review aims to provide a comprehensive summary of the current use of advanced molecular imaging modalities, with a particular focus on PET/CT, for the management of patients with MTC. It aims to guide physicians towards a rationale for the use of molecular imaging also including theranostic approaches and novel therapeutical opportunities. Overall, we emphasize the evolving role of nuclear medicine in MTC. The integration of diagnostics and therapeutics by in vivo molecular imaging represents a major opportunity to personalize treatment for individual patients, with targeted radionuclide therapy being one representative example.

Application of radiomics and machine learning to thyroid diseases in nuclear medicine: a systematic review.

BACKGROUND: In the last years growing evidences on the role of radiomics and machine learning (ML) applied to different nuclear medicine imaging modalities for the assessment of thyroid diseases are starting to emerge. The aim of this systematic review was therefore to analyze the diagnostic performances of these technologies in this setting. METHODS: A wide literature search of the PubMed/MEDLINE, Scopus and Web of Science databases was made in order to find relevant published articles about the role of radiomics or ML on nuclear medicine imaging for the evaluation of different thyroid diseases. RESULTS: Seventeen studies were included in the systematic review. Radiomics and ML were applied for assessment of thyroid incidentalomas at 18 F-FDG PET, evaluation of cytologically indeterminate thyroid nodules, assessment of thyroid cancer and classification of thyroid diseases using nuclear medicine techniques. CONCLUSION: Despite some intrinsic limitations of radiomics and ML may have affect the results of this review, these technologies seem to have a promising role in the assessment of thyroid diseases. Validation of preliminary findings in multicentric studies is needed to translate radiomics and ML approaches in the clinical setting.

Brain positron emission tomography in idiopathic normal-pressure hydrocephalus: new 18 F-fluorodeoxyglucose pattern in a long-known syndrome.

AIM: Patients with idiopathic normal-pressure hydrocephalus (iNPH) can show a global reduction in cerebral glucose metabolism at [ 18 F]Fluorodeoxyglucose (FDG) PET. The presence of caudate hypometabolism has been identified as a potential biomarker in iNPH, yet there is limited evidence of hypermetabolic findings in patients with iNPH so far. METHODS: We retrieved retrospectively patients with iNPH and normal cognitive assessment, evaluated before surgery undergoing brain [ 18 F]FDG-PET. The 18 F-FDG-PET brain scans were compared to those of a control group of healthy subjects, matched for age and sex, by statistical parametric mapping (SPM) to identify areas of relative hypo- and hypermetabolism. Furthermore, the existence of a correlation between areas of hypo- and hypermetabolism in the patient group was tested. RESULTS: Seven iNPH patients (mean age 74 ±â€…6 years) were found in the hospital database. SPM group analysis revealed clusters of significant hypometabolism ( P  = 0.001) in the iNPH group in the dorsal striatum, involving caudate and putamen bilaterally. Clusters of significant hypermetabolism ( P  = 0.001) were revealed in the bilateral superior and precentral frontal gyrus (BA 4, 6). A significant inverse correlation between striatal hypometabolism and bilateral superior and precentral frontal gyrus hypermetabolism was revealed ( P  < 0.001 corrected for multiple comparisons). CONCLUSION: In this cohort, patients with iNPH showed subcortical hypometabolism, including bilateral dorsal striatum. To the best of our knowledge, this is the first report demonstrating a hypermetabolic pattern in the primary motor and premotor areas, and showing an inverse correlation between the striatum and motor cortex in patients with iNPH.

Catastrophic ACTH-secreting pheochromocytoma: an uncommon and challenging entity with multifaceted presentation.

Summary: Cushing's syndrome due to ectopic adrenocorticotropic hormone (ACTH) secretion (EAS) by a pheochromocytoma is a challenging condition. A woman with hypertension and an anamnestic report of a 'non-secreting' left adrenal mass developed uncontrolled blood pressure (BP), hyperglycaemia and severe hypokalaemia. ACTH-dependent severe hypercortisolism was ascertained in the absence of Cushingoid features, and a psycho-organic syndrome developed. Brain imaging revealed a splenial lesion of the corpus callosum and a pituitary microadenoma. The adrenal mass displayed high uptake on both 18F-FDG PET/CT and 68Ga-DOTATOC PET/CT; urinary metanephrine levels were greatly increased. The combination of antihypertensive drugs, high-dose potassium infusion, insulin and steroidogenesis inhibitor normalized BP, metabolic parameters and cortisol levels; laparoscopic left adrenalectomy under intravenous hydrocortisone infusion was performed. On combined histology and immunohistochemistry, an ACTH-secreting pheochromocytoma was diagnosed. The patient's clinical condition improved and remission of both hypercortisolism and catecholamine hypersecretion ensued. Brain magnetic resonance imaging showed a reduction of the splenial lesion. Off-therapy BP and metabolic parameters remained normal. The patient was discharged on cortisone replacement therapy for post-surgical hypocortisolism. EAS due to pheochromocytoma displays multifaceted clinical features and requires prompt diagnosis and multidisciplinary management in order to overcome the related severe clinical derangements. Learning points: A small but significant number of cases of adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome are caused by ectopic ACTH secretion by neuroendocrine tumours, which is usually associated with severe hypercortisolism causing severe clinical and metabolic derangements. Ectopic ACTH secretion by a pheochromocytoma is exceedingly rare but can be life-threatening, owing to the simultaneous excess of both cortisol and catecholamines. The combination of biochemical and hormonal testing and imaging procedures is mandatory for the diagnosis of ectopic ACTH secretion, and in the presence of an adrenal mass, the possibility of an ACTH-secreting pheochromocytoma should be taken into account. Immediate-acting steroidogenesis inhibitors are required for the treatment of hypercortisolism, and catecholamine excess should also be appropriately managed before surgical removal of the tumour. A multidisciplinary approach is required for the treatment of this challenging entity.

[18F]F-Choline PET/CT and 4D-CT in the evaluation of primary hyperparathyroidism: rivals or allies?

Primary hyperparathyroidism is a hard-to-diagnose condition that can run without symptoms for many years without causing symptoms; yet, it can cause dire long-term consequences, such as osteoporosis and renal impairment. First-line diagnostic methods include ultrasound and parathyroid scintigraphy, which provide unsatisfactory results in terms of detection rate. Second-line imaging methods include [18F]F-Choline PET/CT, 4D-CT, and their combination. These methods have shown a great detection rate and sensitivity; however, they are to this day less widespread than the first-line ones. Both the two methods (PET and 4D-CT) have their specific advantages and field of application, as well as their specific limitations. In this narrative review, we will describe the advantages and disadvantages of the two techniques extensively. Moreover, we will try to identify whether the combined examination can play a role and how relevant this role is. Finally, we will try to define the specific clinical situation in which each method can provide the best contribution to diagnosing parathyroid tissue hyperfunction.

Does 18F-Fluorocholine PET/CT add value to positive parathyroid scintigraphy in the presurgical assessment of primary hyperparathyroidism?

Introduction: To investigate the value of presurgical 18F-FCH PET/CT in detecting additional hyperfunctioning parathyroids despite a positive 99mTc-sestamibi parathyroid scintigraphy in patients with primary hyperparathyroidism (pHPT). Methods: This is a retrospective study involving patients with pHPT, positive parathyroid scintigraphy performed before 18F-FCH PET/CT, and parathyroid surgery achieved after PET/CT. Imaging procedures were performed according to the EANM practice guidelines. Images were qualitatively interpreted as positive or negative. The number of pathological findings, their topography, and ectopic location were recorded. Histopathology, Miami criterion, and biological follow-up were considered to ensure effective parathyroidectomy confirming the complete excision of all hyperfunctioning glands. The impact of 18F-FCH PET/CT on therapeutic strategy was recorded. Results: 64/632 scanned pHPT patients (10%) were included in the analysis. According to a per lesion-based analysis, sensitivity, specificity, positive predictive value, and negative predictive value of 99mTc-sestamibi scintigraphy were 82, 95, 87, and 93%, respectively. The same values for 18F-FCH PET/CT were 93, 99, 99, and 97%, respectively. 18F-FCH PET/CT showed a significantly higher global accuracy than 99mTc-sestamibi scintigraphy: 98% (CI: 95-99) vs. 91% (CI: 87-94%). Youden Index was 0.79 and 0.92 for 99mTc-sestamibi scintigraphy and 18F-FCH PET/CT, respectively. Scintigraphy and PET/CT were discordant in 13/64 (20%) patients (49 glands). 18F-FCH PET/CT identified nine pathologic parathyroids not detected by 99mTc-sestamibi scintigraphy in 8 patients (12.5%). Moreover, 18F-FCH PET/CT allowed the reconsideration of false-positive scintigraphic diagnosis (scinti+/PET-) for 8 parathyroids in 7 patients (11%). The 18F-FCH PET/CT influenced the surgical strategy in 7 cases (11% of the study population). Conclusion: In a preoperative setting, 18F-FCH PET/CT seems more accurate and useful than 99mTc-sestamibi scan in pHPT patients with positive scintigraphic results. Positive parathyroid scintigraphy could be not satisfactory before neck surgery particularly in patients with multiglandular disease, suggesting a need to evolve the practice and define new preoperative imaging algorithms including 18F-FCH PET/CT at the fore-front in pHPT patients.